Mbali turned 21 years old this week, but instead of a beer, he got his regular dose of Metamucil.

The lion, who would live about 15 years in the wild, is one of the oldest animals at Reid Park Zoo. His partner, Atatu, is also 21. Their son, Kitabu, is 17.

“Wow,” said Rigel Diaz, 30, who was visiting the zoo with her husband, Paul Diaz, 30, and their 2-month-old son, Diego.

“It’s only fair,” she said of keeping animals into old age. “Otherwise it would be like getting rid of an old dog.”

Besides, she added of the mature Mbali, “He looks so content.”

The lions aren’t the only elders in Reid Park Zoo, or the only senior beasts in zoos across the nation.

Animals are living longer in captivity than ever before, and longer than they would in the wild.

The absence of natural and gun-toting predators, territorial disputes and strenuous activities such as hunting and killing their own food, makes life in the zoo a walk in the park.

Vet care has also improved, leading to longer lifespans through advances in treating the consequences of aging, said Scott Barton, Reid Park Zoo’s general curator.

“Our parents and grandparents just dealt with the pain of growing older, but we now have ways to alleviate the symptoms,” he said. “In zoos, it’s pretty much the same thing. We have better monitoring of the animal’s conditions.”

The Reid Park Zoo, 1030 S. Randolph Way, and Arizona-Sonora Desert Museum, 2021 N. Kinney Road, keep their animals on healthful diets and in naturalistic surroundings, which also contribute to their longevity.

At many zoos, tiny iron cages and bare concrete floors are long gone.

Grassy knolls, shady groves, cliffs, caves, pools and waterfalls have been installed to keep the animals active and content. Playthings keep them occupied.

“Their quality of life has improved dramatically,” Barton said.

Reid Park Zoo habitats are friendly for older and younger creatures alike, which is important because animals stay in the same enclosure their entire lives.

The Desert Museum, which is remodeling some areas to keep animals in the same habitat for their lifespans, often has separate areas out of the public’s view for the older creatures.

Instead of the undulating terrain of their former exhibit, their new off-exhibit pen is stocked with features to help them in their senior years.

“While the exhibit looks really wonderful for people to see,” she said of their former habitat, “it can be difficult for the bears to move about.”

The retirement pen has a pool with gently sloping sides, ramps to a nighttime holding area, stainless-steel scratching posts for bears that no longer can reach around to groom some areas, and feeding chutes so the bears don’t have to move to the opposite side of the pen while they are being fed.

Animals tend to show the same signs of aging found in humans, the curators say.

“We do exactly the same things you might do for one of your own pets or even family members,” Barton said.

In the case of the lions, Atatu’s joints were getting stiff. Mbali, who is deaf, was losing his appetite.

Atatu’s condition is corrected with arthritis medication.

Keepers turn to visual cues if an animal has trouble hearing, audio cues for failing eyesight and other cues, such as scent, to compensate for the loss of other senses.

They stimulate appetites with healthy, special treats.

“Popsicles, meat-sickles, blood-sickles, heart-sickles,” zookeeper Alisha Brewer explained. Scrumptious ingredients, at least for a lion, are frozen in a big bucket for a cool and tasty treat, and their diets are supplemented with ox tails and dead rabbits.

Losing teeth is another sign of old age, one that’s evident in Reid Park’s sun bear, Dresena, who just had a few extracted.

Asian bears usually live to about 20 to 25 in the wild, Barton said. Dresena is going on 29.

“She’s definitely slowing down but she’s in really good health,” he said.

Moms, Reid Park Zoo’s 37-year-old gibbons monkey, is also missing some teeth, not surprising for a primate more than a decade past her prime.

Needing lots of sleep is another sign of senioritis, one exhibited by the zoo’s anteater, Juanita.

“She’s really elderly,” Barton said of the 24-year-old. Anteaters usually live 25 to 30 years.

Until two years ago, Reid Park Zoo had Dave, at 29 the oldest anteater in the country.

“We have a number of different criteria when we feel an animal is longer doing well,” Riplog-Peterson said.

“For instance, if a hummingbird can’t fly, you’re doing it a disservice not to euthanize that animal.”

The most recent euthanization at the Desert Museum was an otter put down last month.

The latest animal put to sleep at Reid Park Zoo was Yebo, a 17-year-old giraffe euthanized last year.

“He was a great animal and certainly a staff favorite,” Barton said. “He was getting arthritic. It got to a point where he just seemed to be very uncomfortable.”

Both zoo and museum officials say it is all about the animals’ quality of life, and the zookeepers’ dedication to being stewards for life.

Care of elderly animals can get expensive, just as it can for people, but curators say it’s a commitment theye made when they took on the animal.

Even with food, medicine, and just about everything else getting more expensive, Brewer said the animals are never slighted.

The renowned San Diego Zoo, which operates both a zoo with smaller enclosures and a wildlife animal park with hundreds of open acres, has the same policy.

In many instances, it also has been the first zoo to learn how long animals can live in captivity. Zoo animals have set many longevity records.

“Geriatrics in wild animal species has not been studied very much,” said spokeswoman Christina Simmons. “When we’re the only zoological organization that has had giant pandas for any length of time, there isn’t anyone to compare them to.”

San Diego has had a giant panda for the past 12 years. The great bears live 14 to 20 years in the wild.

Simmons said breaking ground in animal geriatrics is both exciting and challenging.

“A lot of times, our public doesn’t really understand that signs of geriatrics are a natural part of living,” she said.

One Fort Huachuca family visiting the Reid Park Zoo on Wednesday was amazed that two of the giraffes they were feeding are 19 years old.

“It’s great as long as the animals are kept physically healthy, and mentally healthy, too,” said Kay Hayes, 57, who was visiting Fort Huachuca from Alabama.

Her 40-year-old daughter, Stacy Sandlin, agreed. “It’s wonderful they live to be so old, as long as they’re not forced to just sit there.”